Process of manufacturing acrylic derivatives

ABSTRACT

A process for making acrylic derivatives from acrylic acid and lower esters thereof by dehydrochlorination of the corresponding Alpha -chloropropionic acid or ester in the vapor phase with a catalyst in the presence of added gaseous hydrogen chloride.

United States Patent [191 Berthoux et al.

[451 Jan. 2, 1973 PROCESS OF MANUFACTURING ACRYLIC DERIVATIVESInventors: Jean Berthoux, 69 Decines; Gerard Schneider, 69 Clauire;Renaud de Sui-ville, 92 Bolllogne-Billancourt,

all of France Assignee: PROGIL, Paris, France Filed: July 2, 1971 Appl.No.: 159,535

Foreign Application Priority Data .luly 8, 1970 France ..7026295 US. Cl...260/486 D, 260/526 N Int. Cl..... ..C07c 69/54, C07c 57/04 Fieldofsearch ..260/486 D, 526 N Primary Examiner-Lorraine A. WeinbergerAssistant Examiner-Paul J. Killos v Attorney-Alvin Browdy and SheridanNeimark [5 7 ABSTRACT A process for making acrylic derivatives fromacrylic acid and lower esters thereof by dehydrochlorination of thecorresponding a-chloropropionic acid or ester in the vapor phase with acatalyst in the presence of added gaseous hydrogen chloride.

I 8 Claims, No Drawings PROCESS OF MANUFACTURING ACRYLIC DERIVATIVESThis invention relates to a process of manufacturing acrylic derivativesfrom acrylic acid and its esters by dehydrochlorinating thecorresponding chloropropionic derivatives.

It is known that acrylic acid may be obtained by means of severaldifferent techniques. For example, a well-known process consists indirectly oxidizing propylene with oxygen. According to another techniquewhich is apparently less common and which may be utilized to obtainacrylic acid and its esters, chloropropionic derivatives aredehydrochlorinated in the presence of catalysts. This process does notoffer special difficulties when starting with B- chloropropioniccompounds; however, on the contrary, it is difficult to achieve when thea-isomers are the starting materials because they are difficult todehydrochlorinate. rat-chloropropionic acid is a raw material which ismore readily available than B- chloropropionic acid. However a processdehydrochlorinating a-chloropropionicacid and esters has been describedwhich comprises passing these compounds in the vapor, phase ontocatalysts which are phosphates, sulfates or halides of the group IImetals, these catalysts being in most cases activated; especially whencalcium sulfate is used. However, this process does not yield quitesatisfactory conversion rates and yields. Moreover the relatively hightemperatures used generally 400C. lead to product degradations whichresult in compound losses with tar and carbon formation which in turnfoul the catalyst.

It is accordingly an object of the present invention to provide aprocess which avoids the hereinabove disadvantages and gives highconversion rates of the raw material and quite good yields of thecorresponding acrylic derivatives.

These and other objects are obtained by the present process whichcomprises contacting cit-chloropropionic acid or esters thereof in the Ivapor phase with a dehydrochlorination catalyst of the known type in thepresence of added gaseous hydrogen chloride.

It is surprising that good results are obtained according to thisinvention since hydrogen chloride is per se a product forming during thereaction.

As starting materials there may be used achloropropionic acid or a C toC alkyl ester thereof, such as methyl, ethyl, propyl, isopropyl, etc. Itmay be a pure or a technical product. In the case of achloropropionicacid, for example, the raw product obtained by chlorinating propionicacid, according to known processes, for example in the presence ofphosphorus trichloride as catalyst, and containing, besidescit-chloropropionic acid, low proportions of unreacted .propionic acid,dichloropropionic acid, chloroacetic acid, and optionally traces ofphosphorus derivatives may be used as well as pure 0:- chloropropionicacid recovered by distilling the reaction mixture of propionic acidchlorination.

The quantity of gaseous hydrogen chloride to be used according to theinvention is not an especially critical feature and may vary withinlarge limits. Generally in order to obtain a good conversion rate and nodegradation of the raw material it is advisable ,to use at least about0.2 mole hydrogen chloride for each mole of a-chloropropionic acid orester. Larger quantifor ties may be employed, for example, up to 2 molesof hydrogen chloride for each mole of starting material to bedehydrochlorinated. A molar ratio I-ICl/achloropropionic derivativewhich is higher than 2/1 is not deleterious for the reaction; howeverpreferably such a large quantity of hydrogen chloride is not introducedbecause it results in a commercially less satisfactory process; indeedthis leads to a greater consumption of calories during the process andeventually to the other drawbacks from a practical point of view.

The catalyst may be chosen from among the dehydrochlorination catalystsof known type, especially alkali-earth metal, zinc or magnesiumphosphates and sulfates. Among them, calcium sulfate is preferred. Thesecatalysts are employed in a substantially anhydrous state, unactivated,in the form of granules, the dimensions of which vary, for example, from0.5 to 5 The reaction temperature must be at least sufficient so thatthe a-chloropropionic raw material is substantially maintained in thevapor phase. Practically, the lower temperature limit is about 200C. anda desirable range is between 200 and 350C., preferably 280-3 20 C. It isadvisable not to carry out the reaction above 350C., because, in thiscase, side-reactions take place, such as acid decarboxylation,carbonization, polymerization and tar formation, which result in adecrease in yield and catalyst fouling. Generally, it is carried out atatmospheric pressure although a lower or higher pressure may be applied.

The reaction develops quickly. A residence time equal to or less than 30seconds is in most cases sufficient to give good conversion rates. 7

v In a practical way of achieving the process according to thisinvention, the starting a-chloropropionic material is first vaporized,then admixed with hydrogen chloride, the mixture is further preheated,for example up to the reaction temperature and then is passed through atubular reactor containing the catalyst. It is also possible to preheatthe zit-chloropropionic derivative and hydrogen chloride separatelybefore mixing them. The dehydrochlorinating reaction may also beconducted, using the techniques of a fluidized catalyst. Preferably thereactor is provided with an external heating device, for example amantel in which a heattransfer liquid circulates, in order to maintainthe reactor at the required temperature. When leaving the reactor, thegaseous effluent is cooled to about l5-25C. so that a vapor phase isobtained containing essentially hydrogen chloride, which was initiallyintroduced and formed during the reaction, and a liquid phase comprisingthe desired compound. The gaseous HCl may be recycled to the reaction ina desirable amount. The liquid phase contains some B-chloropr'opionicisomer of the a-chloropropionic derivative used as starting material,which has formed during the reaction by combination of the acrylic acidand HCl and, above all, during the separation of the reactionconstituents; however, this is not a disadvantage in the process becausesuch B-chloropropionic compound can be quantitatively dehydrochlorinatedto the acrylic compound 'by recycling. For that, the hereinabovementioned liquid phase is for example, distilled to separate theacrylicderivative obtained and the distillation'residue which containsB-chloropropionic acid or ester and possibly a small proportion ofunreacted a-chloropropionic isomer, is recycled to thedehydrochlorination reaction. It is also possible to distill all theliquid phase before recycling the chloropropionic fraction.

The following examples illustrate the process according to theinvention. The parts and percentages are given by weight.

EXAMPLE 1 In a tubular reactor filled'with 360 parts of anhydrouscalcium sulfate granules and maintained at 300C., there was introducedper hour a mixture of 12 parts gaseous HCl and 125 partsa-chloropropionic acid containing 0.2 percent propionic acid, 0.2percent a,a-dichloropropionic acid I and 0.1 percent monochloroaceticacid. The molar ratio HCl/organic feed was thus 0.29. Thea-chloropropionic acid had been vaporized, admixed with HCl and themixture heated to the reaction temperature before entering the reactor.The residence time in the apparatus was 17 seconds. When leaving thereaction zone, the gaseous effluent was cooled and there were recovered,per hour, 43.1 parts gaseous l-lCl and 91 parts of a liquid phasegiving, by distillation, 63.4 percent acrylic acid, 33 percentB-chloropropionic acid, 1.7 percent achloropropionic acid, the residuebeing polymers.

The a-chloropropionic acid conversion rate was 98.8 percent. SinceB-chloropropionic acid may be quantitatively converted into acrylicacid, as explained above, this was taken into account in the calculationof the yield of desired product which is thus 95.2 percent with regardtothe reacted raw material.

After 20 hours running under the hereinabove conditions, there wasobserved no fouling nor loss in efficiency of the catalyst.

EXAMPLE 2 The procedure of example 1 was followed with the same startingmaterial, but using, for each hour, 45.6 parts gaseous hydrogen chloridefor 136 parts of acid.

The molar ratio HCl/organic feed was 1/1. The re- EXAMPLE 3 Theprocedure of the foregoing examples was followed but introducing intothe reactor 47.5 parts HCl/hour and 140 parts/hour of an organic feedcomprising 35 percent /3-chloropropionic acid and 63 percentB-chloropropionic acid, this later coming from a formerdehydrochlorinating operation according to the invention (the reminderto 100 percent was high-boil- 4 ing compounds). The residence time was12 seconds at a temperature of 300C.

There was recovered from the gaseous effluent leaving the reactor, foreach hour, 81.6 parts of HCl and parts of a liquid organicphasecontaining 5.3 ercent a-chloropropionic acid, 28.8 percent 0 ,8-

chloropropionic acid and 57.4 percent of acrylicacid. TheB-chloropropionic acid which formed during the reaction was used in afurther operation.

EXAMPLE 4 There was introduced into a reactor containing calcium sulfateand maintained at 300C., a mixture, preheated in accordance with Example1, of 65.7 parts HCl/hour and 134 parts/hour of a raw achloropropionicacid containing 4.3 percent aadichloropropionic acid, 1.1 percentpropionic acid, 0.1 percent acetic acid, 0.4 percent monochloraceticacid and 0.4 percent phosphorus derivatives. The molar ratioHCl/a-chloropropionic acid was 1.55/1. The residence time in the reactorwas 9 seconds.

There was recovered, after the reaction, 80.3 parts gaseous l-lCl/hourand 1 1 1 parts/hour of a liquid phase containing 22.8 percent acrylicacid, 12.2 percent B- chloropropionic acid and 62.0 percentachloropropionic acid.

The conversion. rate of the starting achloropropionic acid was 45.3percent and the yield of acrylic and B-chloropropionic acids was 91.1percent.

It will be obvious to those skilled in the art that various changes maybe made without departing from the scope of the invention and theinvention is not to be considered limited to what is described in thespecification.

What is claimed is:

1. In a process of manufacturing acrylic derivatives selected from thegroup consisting of acrylic acid and C to C alkyl esters thereof bydehydrochlorinating the corresponding a-chloropropionic acid or estersin the vapor phase with a catalyst, the improvement which comprisesconducting the reaction in the presence of added gaseous hydrogenchloride.

2. A process according to claim 1 wherein the quantity of added hydrogenchloride is between 0.2 to 2 moles for each mole of a-chloropropionicacid or ester.

3. A process according to claim 1 wherein the catalyst is used in theanhydrous state and is selected from the group consisting ofearth-alkali metal, zinc and magnesium phosphates and sulfates.

4. A process according to claim 3 wherein the catalyst is calciumsulfate.

5. A process according to claim 1 wherein the reaction temperature isbetween 200C. and 350C.

6. A process according to claim 5 wherein the reaction temperature isbetween 280C. and 320C.

7. A process according to claim 1 wherein the gaseous effluent from thereaction is cooled in order to separate gaseous hydrogen chloride and aliquid phase containing said acrylic acid or ester.

8. A process according to claim 1 wherein any B- chloropropionic acid orester which has formed during the reaction is recycled to thedehydrochlorinating zone.

2. A process according to claim 1 wherein the quantity of added hydrogenchloride is between 0.2 to 2 moles for each mole of Alpha-chloropropionic acid or ester.
 3. A process according to claim 1wherein the catalyst is used in the anhydrous state and is selected fromthe group consisting of earth-alkali metal, zinc and magnesiumphosphates and sulfates.
 4. A process according to claim 3 wherein thecatalyst is calcium sulfate.
 5. A process according to claim 1 whereinthe reaction temperature is between 200*C. and 350*C.
 6. A processaccording to claim 5 wherein the reaction temperature is between 280*C.and 320*C.
 7. A process according to claim 1 wherein the gaseouseffluent from the reaction is cooled in order to separate gaseoushydrogen chloride and a liquid phase containing said acrylic acid orester.
 8. A process according to claim 1 wherein any Beta-chloropropionic acid or ester which has formed during the reaction isrecycled to the dehydrochlorinating zone.